Conveying device for sheets

ABSTRACT

Device for the conveying of sheets from each of a plurality of sheet piles via a partially common conveyor track. This track extends in vertical direction along superposed stock holders. Adjacent to the sheet delivery side a driven roller is stationarily arranged above each pile. Each of these rollers can function both as suction roller for separating sheets from a pile and as friction roller for conveying sheets in the common track. For separating sheets from a pile, each pile can be brought by pneumatic means into short contact with a driven roller then functioning as a suction roller. For conveying sheets in the common track, each roller cooperates with a pressure roller. After a sheet in the common track has been gripped between a driven roller and a pressure roller, the sucting action of that driven roller is interrupted.

The invention relates to a device for the conveying of sheets to aprocessing station, comprising at least two stock holders for sheetpiles, in which each sheet pile is provided with a separation rollerwhich can be activated selectively in order to convey a sheet from astock holder to a processing station, and conveyor tracks provided withconveyor elements which connect the stock holders to the processingstation.

Such a device is known from the Netherlands patent application No.7404899.

A device is described therein which is provided with a number of stockholders with means forming part of each stock holder to separate a sheetfrom the pile included therein and means to convey that sheet to anexposure station. The feed from the various stock holders to theexposure station is effected according to the abovementioned Netherlandspatent application No. 7404899 via entirely separated conveyor tracks.The feed of sheets via entirely separated conveyor tracks has as adisadvantage that a large number of conveyor and driving means arerequired, which requires a complicated sheet feeding system requiring alot of space.

The object of the invention is to provide a conveying device for sheetswhich does not have the abovementioned disadvantage, and which is ableto convey sheets with a relatively small number of conveyor and drivingmeans from one of a number of stock holders to a processing station.

According to the invention this object is achieved in that the conveyortrack for each stock holder which is situated nearer to the processingstation coincides with a part of the conveyor track for each holdersituated further away from the processing station, in that the conveyorelements at least partially consist of roller pairs of which each timethe driven roller is formed by a separation roller and in that when oneseparation roller is activated, all rollers are driven in a rotatingway. In this manner it is achieved that with a relatively small numberof conveyor and driving means sheets from one of a number of stockholders can be conveyed to a processing station in such a way that asimple sheet feeding system taking little space is created.

Preferably, each separation roller in a non-activated position is not incontact with the sheet pile and means are available which when theseparation roller is activated, effect a contact between the separationroller and the sheet pile.

In this way it is achieved that with simple means it is guaranteed thatsheets can only be fed from the selected stock holder.

Preferably the sheet pile at least partially rests on a movable platewhich has been fitted against a wall of a space which can be connectedto a compressed air source and discharge openings are formed in thewall.

In this way it is achieved that each separation roller can be installedin a fixed position and that the sheet pile forming part of theactivated separation roller can only come into contact with theseparation roller during excitation by compressed air.

Preferably the separation roller is formed by a suction roller. In thisway it is achieved that during the separation a sheet can simply be keptin contact with a circumferential part of the separation roller in orderto be able to branch off the sheet in the conveyor track formed byroller pairs.

Preferably the suction roller is formed by a hollow cylindrical tubewhich on the outer surface is provided with a coating in which a numberof borings have been fixed, the borings being connected to the spaceinside the hollow tube via a number of saw cuts fitted perpendicularlyto the axis of the tube, of a depth which is smaller than half thediameter of that tube.

In this way it is achieved that a simple constructed suction roller isobtained which at the same time can function as a friction conveyorroller.

Other characteristics and advantages of the invention will become clearfrom the description given below of a preferred embodiment referencebeing made to the attached drawings, in which:

FIG. 1 is a diagrammatic cross section of a number of stock holderssituated above one another,

FIG. 2 is a diagrammatic cross section of a part of anelectrophotographic copying machine, in which a device for the conveyingof sheets according to the invention, can be used,

FIG. 3 is a cross section of a stock holder with connected air pressuresystem,

FIG. 4 is a longitudinal section of a separation roller,

FIG. 5 is a cross section of a separation roller according to line V--Vof FIG. 4, and

FIG. 6 is a slide axially shifted in two positions which can be fittedin a separation roller.

FIG. 1 shows a cross section of a number of stock holders 1, 2, 3 and 4situated above one another, in each whereof a pile of sheets can beaccomodated. The stock holders can be arranged for acceptance of sheetpiles of different sizes, for example of sizes A4, A3, A2 and A1.

In fixed positions, at some distance above the discharge side of eachsheet pile a separation roller 5, 6, 7 and 8, respectively is mounted.These separation rollers are, when the device is in operation, driven ina rotating way and are able, in the manner described below, to dischargesheets from a pile and to supply to a joint conveyor track 9 whichextends almost vertically alongside the discharge side of the stockholders. The conveying of sheets in this conveyor track is obtained bypressure rollers 10, 11, 12 and 13 which cooperate with the drivenseparation rollers 5, 6, 7 and 8 respectively and form roller pairs withthese respectively.

As shown in FIG. 2, which represents an electro-photographic copyingmachine in which the invention can be applied, the separation rollers 5,6, 7 and 8 are driven simultaneously via a joint drive element 14 whichis kept in motion by a drive motor 15 when the device is switched on. Asheet supplied by the abovementioned roller via conveyor track 9 is fedto an endless conveyor belt 16 which extends horizontally above thestock holders. Conveyor belt 16 can be driven in two directions by motor15 via a transmission and drive element 17.

The flat part directed upwards of conveyor belt 16 forms the exposureplace of fed photoconductive receiving sheets. A charging unit 18 isplaced above the conveyor belt 16 in a fixed position which is situatedupstream of the exposure place. When the charging unit is in operation afed photoconductive receiving sheet reaches the exposure place in acharged condition. The receiving sheet is kept in the desired exposureposition by interrupting the drive of conveyor belt 16.

By means of an optical system not-shown an image of an original, forinstance a microfilm, can be projected onto a receiving sheet positionedin the exposure plane in order to form a latent electrostatic imagethereon. Upon further conveying from the exposure position the receivingsheet is guided part a developing device 19 in order to develop thelatent charge image.

In order to enable the operator to carry out the optical adjustment on asheet positioned in the exposure position it is desirable that aphotoconductive receiving sheet can be brought into the exposureposition in an uncharged condition.

After this adjustment has been carried out, the receiving sheetconcerned can still be charged by moving the conveyor belt in theopposite direction until the receiving sheet has passed the chargingdevice entirely, after which the receiving sheet, with the charging unitswitched on, is again fed to the same exposure position. In order toavoid during the returning conveyance that the receiving sheet arrivesin the vertical conveyor track 9, a branching element 20 is brought intothe dotted-line position during this conveyance. At the same time an airstream from space 21 is directed at the receiving sheet in order toguide it over a plate 22 which has been fitted underneath the conveyorbelt 16. In an alternative way during the returning conveyance thereceiving sheet may be guided along a vertical guide track parallel tothe conveyor track 9. By these means branching element 20 and air supplyfrom space 21 can be avoided. After exposure of a charged receivingsheet, conveyor belt 16 takes the receiving sheet provided with a latentimage to a developing device 19, after which the finished copy leavesthe copying machine.

The position which a receiving sheet can occupy in the exposure plane isadjustable, for instance depending on the size of the fed receivingsheet or on the desired position of the projected image on the receivingsheet.

Seen in the direction of movement a positioning is obtained by stoppingthe movement of the conveyor belt 16 at the moment that the receivingsheet has reached the desired position.

In the direction perpendicular to the direction of movement apositioning can be obtained by fixing the stock holders in the copyingmachine movably in that direction.

The effective operating area of the separation rollers, 5, 6, 7 and 8respectively, mounted in a fixed position can be brought in accordancewith the occupied position of the sheet pile in question in a mannerdescribed below on the basis of FIGS. 4, 5 and 6.

The stock holders can if necessary be moved in a transverse direction upto outside the machine, in order to make them accessible for putting ina new pile.

The new invention will now be further described on the basis of FIG. 3,which shows a stock holder. The other stock holders are built upanalogously.

Each stock holder is formed by a bottom plate 23 and a raised edge 25 onthe discharge side.

The bottom plate is provided with openings 24 near the discharge side.An expandable air bag 24A is connected to the upper side of the bottomplate 23 and communicates via openings 24 to space 26. Part of thebottom plate 23 and the raised edge are double-walled to form theenclosed space 26. This space is limited on the underside by a V-shapedpart 27 which is provided with openings 28. Raised edge 25 is providedwith openings 29 in the wall directed to the pile and in fact at theheight of the upper side of an inserted sheet pile. The stock holder canslide with the V-shaped part 27 over a cylinder 30 fitted in a fixedposition and which is provided with openings 31. These openings 31 formtogether with openings 28 a connection between cylinder 30 and space 26.The cylinder is, via a compressed air line, connected with a compressedair source 33, so that via openings 31 and 28 an increased air pressurecan be achieved in space 26.

With bottom plate 23 a cover plate 32 is connected by hinges. The hingescan be formed by a flanged edge 32A of the cover plate, which protrudesthrough openings fitted in the bottom plate. Cover plate 32 carries theinserted pile or a part of the inserted pile. When an increased airpressure is effected in space 26, the air flowing through openings 24will press up cover plate 32, as a result of which the top sheet of thepile resting on this will be brought into contact with separation roller5, 6, 7 or 8 placed in a fixed position above the pile. At the sametime, via openings 29 in the raised edge 25 of the stock holder, air canbe blown against the front of the pile in order to detach the leadingedges of the sheets from one another.

Each separation roller 5, 6, 7 and 8 is arranged to keep a sheet byunderpressure by connecting each roller with the suction line of theabove-mentioned compressed air source 33.

According to FIGS. 4 and 5 each separation roller is built up from ahollow cylindrical tube 34 provided with openings 35 obtained by sawcuts and covered by a sheath 36 of resilient material, for examplerubber, provided with openings 37 which are connected to openings 35 inthe tube. One tube end is linked to the suction line of compressed airsource 33 in order to create underpressure in the roller. A roller thusbuilt up may function as a friction conveyor roller and as a suctionconveyor roller.

Each separation roller is preferably of the same length. This has itsadvantages in connection with the manufacture and assembly between thesame frame plates inside a copying machine. If a separation roller hasto cooperate with a narrower sheet pile, the suction width of theseparation roller to the pile width may be limited by bringing a hollowcylindrical slide 38 into the roller. This slide shown in FIG. 6 in twopositions is provided with slots 39 running parallel to the rotationaxis at the length of the pile width. Only at the places of these slotsthe separation roller will be able to work as a suction conveyor roller.By axial shifting of the slide in the separation roller the suction areaof the separation roller can be shifted depending upon the position ofthe stock holder.

On the basis of FIG. 3 the removal of a receiving sheet from the pile inaccordance with the invention will now be described.

A compressed air source creates simultaneously an underpressure in line40 and an overpressure in line 41. When a sheet has to be removed fromthe pile, two valves 42A en 42B are simultaneously opened in valve block42 in order to effect simultaneously an underpressure in one of theseparation rollers 5, 6, 7 or 8 and an overpressure via one of thecylinders 30 in a space 26.

As a result of an increase of the air pressure in this space 26 thecover plate 32 moves upwards, so that the pile resting thereon comesinto contact with a separation roller 5, 6, 7 or 8, in which at thatmoment there is an underpressure. The separation roller sucks the topsheet when the openings situated in an axial line therein come intocontact with that sheet. Via openings 29 in the raised edge 25 of thestock holder air is simultaneously blown against the discharge side ofthe pile in order to prevent that more than one sheet is carried off bythe separation roller. Then the valve 42B is closed as a result of whichthe pile returns again to its original position. The separation rollerkeeps one sheet sucked up for at least one quarter of a revolution untilthe leading edge has come into contact with the pressure roller whichcooperates with the separation roller. At that moment the valve 42A invalve block 42 is closed, as a result of which the separation roller nolonger functions as a suction roller. The roller pairs formed by aseparation roller and a pressure roller operate further as frictionconveyor rollers in order to convey receiving sheets taken from pilessituated lower to a processing station.

It is clear that the invention is not restricted to the embodimentdescribed above, but that within the framework of the invention numerousmodifications are possible. It is possible, for instance, to effect thebriefly required overpressure in space 26 and the simultaneously brieflyrequired underpressure in one of the separation rollers 5, 6, 7 or 8 indifferent manners, for instance by effecting air displacement by meansof a plunger.

We claim:
 1. An apparatus for conveying sheets to a processing station,comprising: a plurality of sheet stack holders spaced apart along aconveyor path leading to said processing station; conveyor means fordelivering a sheet from a stack on any selected one of said holders intosaid path and then along said path to said station, said conveyor meansincluding a plurality of roller pairs mutually spaced apart along saidpath, each of said pairs comprising two relatively fixed rollers forminga nip to advance along said path a sheet gripped in the nip, with oneroller of each pair disposed in part over a said stack holder and beingselectively activatable to serve as a separation roller for feeding asheet from the stack holder into said path; the portion of said paththat leads from each stack holder situated nearer to said processingstation coinciding with a portion of said path that leads from eachstack holder situated farther from said processing station; means forbringing a sheet stack on any selected one of said holders and therelated separation roller in engagement and for activating that rollerso as to feed a sheet from that stack into said path; and means operablewhen one of said separation rollers is activated to rotate all rollersof said pairs in unison.
 2. An apparatus according to claim 1, saidconveyor path being substantially vertical and each of said sheet stackholders being disposed substantially horizontally and transverse to saidconveyor path.
 3. An apparatus according to claim 1, each said stackholder comprising a movable plate for at least partially supporting asheet stack, and comprising pneumatic means including an airexpansiblechamber adjacent to said plate and means for admitting compressed airinto said chamber to expand it and thereby displace said plate so as toeffect said engagement.
 4. An apparatus according to claim 3, saidpneumatic means including an air space bounded in part by a wall havingopenings therein for passage of compressed air therethrough into saidchamber and said plate being pivotable relative to said wall in responseto the admission of compressed air into said chamber through saidopenings.
 5. An apparatus according to claim 1, 3 or 4, each of saidseparation rollers comprising means for holding a sheet to its surfaceby suction.
 6. An apparatus acording to claim 5, each of said separationrollers comprising a hollow cylindrical tube the wall of which is formedwith recesses spaced apart therealong and extending therethrough andtransverse to its axis, with a resilient outer surface layer overlyingsaid tube and openings communicating with said recesses, the depth ofsaid recesses being less than half the diameter of said tube.
 7. Anapparatus according to claim 4, each of said separation rollers beingconnectable to a suction line of a compressed air source that has apressure line connectable to lead compressed air to a said air space. 8.An apparatus for conveying sheets to a processing station, comprising: aplurality of sheet stack holders spaced apart along a conveyor pathleading to said processing station, each sheet stack holder comprising amovable plate for at least partially supporting a sheet stack and meansincluding an air space adjacent to said plate for receiving air underpressure to displace said plate and thereby dispose a sheet stackthereon in sheet feeding position; conveyor means for delivering a sheetfrom a stack on any selected one of said holders into said path and thenalong said path to said station; said conveyor means including aplurality of roller pairs mutually spaced apart along said path, each ofsaid pairs comprising two relatively fixed rollers forming a nip toadvance along said path a sheet gripped in the nip, with one roller ofeach pair being disposed in part over a said stack holder and beingselectively activatable to serve as a separation roller for feeding asheet from the associated sheet holder into said path, each saidseparation roller comprising means for holding a sheet to its surface bysuction, the portion of said path that leads from each stack holdersituated nearer to said processing station coinciding with a portion ofsaid path that leads from each stack holder situated farther from saidprocessing station; means for selectively activating any one of saidseparation rollers, including means for applying suction to the selectedroller and means for admitting compressed air to the said spaceassociated with that roller to displace the associated movable plate andeffect contact between the selected separation roller and a sheet on itsassociated sheet stack; and means operable to rotate all rollers of saidroller pairs in unison when one of said separation rollers is activated.9. An apparatus according to claim 8, each of said separation rollerscomprising a resilient surface effective to frictionally engage andadvance a sheet being conveyed.
 10. An apparatus according to claim 8,each said separation roller comprising means to prevent the applicationof suction to a sheet at that portion of the surface of the separationroller which lies in the conveyor path at the side of the nip of theroller pair toward the processing station.
 11. An apparatus according toclaim 8, said conveyor path being substantially vertical and each ofsaid sheet stack holders being disposed substantially horizontally andtransverse to said conveyor path.
 12. An apparatus according to claim 8,each said air space being defined in part by a wall having openingstherein for passage of compressed air therethrough and the associatedstack supporting said plate is movable being displaceable relative tosaid wall to sheet feeding position in response to the admission ofcompressed air into said air space through said openings.
 13. Anapparatus according to claim 8, each of said separation rollerscomprising a hollow cylindrical tube the wall of which is formed withrecesses spaced apart therealong and extending therethrough andtransverse to its axis, with a resilient outer surface layer overlyingsaid tube and formed with openings communicating with said recesses, thedepth of said recesses being less than half the diameter of said tube.14. An apparatus according to claim 8, 12 or 13, each of said separationrollers being connectable to a suction line of a compressed air sourcethat has a pressure line connectable to lead compressed air to a saidair space.